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梶田 遥一*; 永井 隆之*; 山岸 茂直*; 木村 健太*; 萩原 雅人; 木村 剛*
Chemistry of Materials, 36(15), p.7451 - 7458, 2024/08
Ferroaxial transitions of NaBa
(PO
)
(
= Mg, Mn, Co, and Ni) with the glaserite structure, featuring rotational distortions of PO
tetrahedra, are investigated. Neutron powder diffraction (NPD) measurements on polycrystalline samples were carried out in the temperature range from room temperature to 800 K. Structure analyses on the NPD data revealed that all of the compounds studied here have a ferroaxial structure (space group:
)at room temperature and undergo a ferroaxial transition into a non-ferroaxial phase (space group:
1) upon heating. Structural parameters change continuously at the transition temperature, which suggests that the ferroaxial transition of Na
Ba
(PO
)
systems is of the second order. Furthermore, to examine the structural stability, ab initio phonon calculations were carried out for Na
BaMg(PO
)
. The calculated result shows that the rotational phonon mode instability inherent in the non-ferroaxial
1 phase leads to the
phases as a ground state, which well explains the experimental result. This study revealed that Na
Ba
(PO
)
systems with the glaserite structure are a class of ferroaxial compounds showing a second-order pure ferroaxial transition.
山岸 茂直*; 林田 健志*; 三澤 龍介*; 木村 健太*; 萩原 雅人; 村田 智城*; 廣瀬 左京*; 木村 剛*
Chemistry of Materials, 35(2), p.747 - 754, 2023/01
被引用回数:5 パーセンタイル:86.76(Chemistry, Physical)The so-called "ferroaxial transition" characterized by a rotational structural distortion that breaks a mirror symmetry has gained growing interest in terms of a new class of ferroic state in crystalline materials. RbFe(MoO)
which belongs to glaserite-type compounds, X□;1 Y□;2 [M(TO
], is one of the most representative materials showing a ferroaxial transition, i.e., ferroaxial materials. Considering a variety of glaserite-type compounds, we expect that they provide a good arena for ferroaxial materials. In this work, we explored new ferroaxial materials by formula-based screening using regular expression search and symmetry detection algorithm. As a result, we found that a glaserite-type compound, K
Zr(PO
)
, is one of the promising candidates for ferroaxial materials. Experimentally, we demonstrate that K
Zr(P O
)
shows a ferroaxial transition at about 700 K, which is well explained by ab initio phonon calculations. The ferroaxial nature of K
Zr(PO
)
is further confirmed by the observation of its domain structures using a linear electrogyration effect, that is, optical rotation in proportion to an applied electric field. Our work provides an effective approach to exploring ferroaxial materials.
林田 健志*; 上村 洋平*; 木村 健太*; 松岡 悟志*; 萩原 雅人; 廣瀬 左京*; 盛岡 仁*; 長谷川 達夫*; 木村 剛*
Physical Review Materials (Internet), 5(12), p.124409_1 - 124409_10, 2021/12
被引用回数:17 パーセンタイル:76.86(Materials Science, Multidisciplinary)The ferroaxial order, which is characterized by a rotational structural distortion in a crystal, has been recently proposed as one of ferroic orders. Though the domain formation is a characteristic feature in ferroic materials, there has been little study done concerning that for the ferroaxial order. Here, we investigate ferroaxial domains that are formed through a ferroaxial transition in two representative ferroaxial materials, NiTiO and RbFe(MoO
)
. We spatially resolve their domain structures using an optical method based on electric-field- induced optical rotation, that is, electrogyration (EG). In NiTiO
, multi-domains are constructed when crystals undergo a ferroaxial transition and the domain size depends on the cooling rate around the transition temperature. Furthermore, the ferroaxial domain structure obtained by the EG measurement is well matched with that by scanning X-ray diffraction (XRD). RbFe(MoO
)
also exhibits multi-domain states in which domain patterns are different each time a crystal undergoes a ferroaxial transition. In addition, the temperature dependence of the EG signal well obeys that of the order parameter of a first-order phase transition. These results ensure the effectiveness of the EG effect to elucidate the nature of ferroaxial order.
木村 健太*; 八木 直輝*; 長谷川 舜介*; 萩原 雅人; 三宅 厚志*; 徳永 将史*; Cao, H.*; 益田 隆嗣*; 木村 剛*
Inorganic Chemistry, 60(20), p.15078 - 15084, 2021/10
被引用回数:1 パーセンタイル:9.44(Chemistry, Inorganic & Nuclear)In materials showing a linear magnetoelectric (ME) effect, unconventional functionalities can be anticipated such as electric control of magnetism and nonreciprocal optical responses. Thus, the search of new linear ME materials is of interest in materials science. Here, using a recently proposed design principle of linear ME materials, which is based on the combination of local structural asymmetry and collinear antiferromagnetism, we demonstrate that an anion-deficient fluorite derivative MnTa
O
is a new linear ME material. This is evidenced by the onset of magnetic-field-induced electric polarization in its collinear antiferromagnetic phase below
= 24 K. Furthermore, we also find an antiferroelectric-like phase transition at
= 55 K, which is attributable to an off-center displacement of magnetic Mn
ions. The present study shows that Mn
Ta
O
is a rare material that exhibits both ME and antiferroelectric-like transitions. Thus, Mn
Ta
O
may provide an opportunity to investigate the physics associated with complicated interactions between magnetic (spin) and electric dipole degrees of freedom.
Shikin, A. M.*; Estyunin, D. A.*; Klimovskikh, I. I.*; Filnov, S. O.*; Kumar, S.*; Schwier, E. F.*; 宮本 幸治*; 奥田 太一*; 木村 昭夫*; 黒田 健太*; et al.
Scientific Reports (Internet), 10, p.13226_1 - 13226_13, 2020/08
被引用回数:59 パーセンタイル:96.07(Multidisciplinary Sciences)Modification of the gap at the Dirac point (DP) in axion antiferromagnetic topological insulator MnBiTe
and its electronic and spin structure have been studied by angle- and spin-resolved photoemission spectroscopy (ARPES) under laser excitation at various temperatures, light polarizations and photon energies. We have distinguished both large and reduced gaps at the DP in the ARPES dispersions, which remain open above the N
el temperature of
= 24.5 K. We propose that the gap above
remains open due to a short-range magnetic field generated by chiral spin fluctuations. Spin-resolved ARPES, XMCD and circular dichroism ARPES measurements show a surface ferromagnetic ordering for the large gap sample and apparently significantly reduced effective magnetic moment for the reduced gap sample.
廣瀬 健太郎; 西尾 勝久; 牧井 宏之; 西中 一朗*; 太田 周也*; 永山 達郎*; 田村 信行*; 後藤 真一*; Andreyev, A. N.; Vermeulen, M. J.; et al.
Nuclear Instruments and Methods in Physics Research A, 856, p.133 - 138, 2017/06
被引用回数:5 パーセンタイル:43.75(Instruments & Instrumentation)Fission and capture reactions were simultaneously measured in the neutron-induced reactions of Am at J-PARC. Data were taken with the TOF method in
= 0.1
20 eV. The fission events were observed by detecting prompt fission neutrons using liquid organic scintillators. The capture reaction was measured by detecting
rays from the compound nuclei using the same detectors, where the prompt fission neutrons and capture
rays were separated by a pulse shape analysis. The cross sections were obtained by normalizing the relative yields at the first resonance to evaluations or other experimental data. The ratio of the fission to capture cross sections at each resonance is compared with those from an evaluated nuclear data library and other experimental data. Some differences were found between the present values and the library/literature values at several resonances.
片渕 竜也*; 松橋 泰平*; 寺田 和司; 井頭 政之*; 水本 元治*; 廣瀬 健太郎; 木村 敦; 岩本 信之; 原 かおる*; 原田 秀郎; et al.
Physical Review C, 91(3), p.037603_1 - 037603_5, 2015/03
被引用回数:8 パーセンタイル:50.32(Physics, Nuclear)Time-of-flight spectra of the neutron capture events of Nd were measured using a spallation neutron source at the Japan Proton Accelerator Research Complex. The first six resonances of
Nd reported in a previous work were not observed. The experimental results and cross-search of resonance energies in nuclear data libraries suggested that resonances of impurity nuclide
Pr have been mistakenly assigned as
Nd in the previous experiment. To investigate the impact of non-existence of the resonances to the s-process nucleosynthesis model, the Maxwellian averaged neutron capture cross sections with and without the misassigned resonances were compared.
原 かおる; 後神 進史*; 原田 秀郎; 廣瀬 健太郎; 木村 敦; 金 政浩*; 北谷 文人; 小泉 光生; 中村 詔司; 藤 暢輔; et al.
JAEA-Conf 2014-002, p.88 - 92, 2015/02
Recently, neutron shields of a large Ge detector array at the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) in the Japan Proton Accelerator Research Complex (J-PARC) were modified to suppress the background from boron rubber sheets to enriched LiF tiles. For the new experimental set-up, efficiencies and response functions of the cluster Ge detectors with the BGO anti-coincidence detectors were measured with
-rays from standard sources and prompt
-rays from the
Si(n,
) and
Cl(n,
) reactions. The simulation parameters were adjusted with the EGS5 code so as to reproduce the data set of efficiencies and response functions. Based on this information, a pulse height weighting function will be deduced in the energy range of 0.1-10 MeV.
木村 敦; 廣瀬 健太郎; 中村 詔司; 原田 秀郎; 原 かおる; 堀 順一*; 井頭 政之*; 加美山 隆*; 片渕 竜也*; 木野 幸一*; et al.
Nuclear Data Sheets, 119, p.150 - 153, 2014/05
被引用回数:5 パーセンタイル:37.68(Physics, Nuclear)The neutron-capture cross sections of Sn and
Sn were measured by the time-of-flight method in the energy range from 10 meV to 2 keV with an array of germanium detectors in ANNRI at J-PARC. The preliminary results of the neutron-capture cross sections for
Sn and
Sn were obtained by normalizing the relative cross sections to the thermal cross section measured by Krane and to the evaluated value of JENDL-4.0 at the 47.05-eV resonance, respectively. Twelve new resonances for
Sn were observed, whereas the 21.02-, 40.38- and 166-eV resonances for
Sn and the 289-eV resonance for
Sn which are listed on JENDL-4.0 and/or ENDF/B VII.1 were not observed. The prompt
-ray distributions gated at the
Sn and
Sn resonances were obtained. Twenty-three new prompt
-ray emissions were observed in the
Sn (n,
) reactions.
堀 順一*; 八島 浩*; 中村 詔司; 古高 和禎; 原 かおる; 原田 秀郎; 廣瀬 健太郎; 木村 敦; 北谷 文人; 小泉 光生; et al.
Nuclear Data Sheets, 119, p.128 - 131, 2014/05
被引用回数:4 パーセンタイル:32.67(Physics, Nuclear)本研究では、Seと
Seの中性子共鳴からの捕獲
線を測定した。
Seは、簡単な殻模型から2p
軌道まで中性子が占有されている偶-偶核であるので、プライマリ
線遷移の始状態と終状態間の強い相関が予想される。
Seは、安定Se同位体の中で唯一の奇数核であるので、同じ奇数核である
Seの評価に資する情報を含んでいると期待される。J-PARC、物質・生命科学実験施設(MLF)の中性子核反応実験装置(ANNRI)に整備した4
Geスペクトロメータを用いて、飛行時間法により測定を行った。
Seの27eV共鳴、及び
Seの113eV, 212eV, 291eV, 342eV, 690eV及び864eV共鳴に対応する
線波高スペクトルを得た。これらのプライマリ遷移
線の相対強度を求め、報告されている実験データと比較を行った。
Seの27eV共鳴について、293keV準位への強いプライマリ遷移が観測された。
Seについては、共鳴ごとに全く異なる崩壊パターンを見いだした。
廣瀬 健太郎; 古高 和禎; 原 かおる; 原田 秀郎; 堀 順一*; 井頭 政之*; 加美山 隆*; 片渕 竜也*; 木村 敦; 金 政浩*; et al.
Nuclear Data Sheets, 119, p.48 - 51, 2014/05
被引用回数:1 パーセンタイル:10.14(Physics, Nuclear)The cross section of the Np
reaction has been measured in an energy range from 10 meV to 1 keV at the Japan Proton Accelerator Research Complex (J-PARC). The NaI(Tl) spectrometer installed in the accurate neutron-nucleus reaction measurement instrument (ANNRI) was used for the measurement. The relative cross section was obtained using the neutron spectrum measured by the
B
reaction. The absolute value of the cross section was deduced by normalizing the relative cross section to the evaluated value in JENDL-4.0 at the first resonance. In this presentation, the obtained results for the cross section, the Westcott factor and the resonance analysis are reported. This work was supported by JSPS KAKENHI Grant Number 22226016.
中村 詔司; 木村 敦; 北谷 文人; 太田 雅之; 古高 和禎; 後神 進史*; 原 かおる; 原田 秀郎; 廣瀬 健太郎; 金 政浩*; et al.
Nuclear Data Sheets, 119, p.143 - 146, 2014/05
被引用回数:10 パーセンタイル:56.90(Physics, Nuclear)長寿命放射性核種Pd、及び不純物として含まれている安定核種
Pdの中性子捕獲断面積を測定した。J-PARCの物質・生命科学実験施設(MLF)のBL04に整備された中性子核反応実験装置(ANNRI)を用いて、飛行時間法により熱領域から300eVの中性子エネルギーに対して、中性子捕獲断面積を測定した。報告されていた幾つかの共鳴が、
Pdに起因しないことなど、共鳴に関する新たな知見が得られた。
原田 秀郎; 太田 雅之; 木村 敦; 古高 和禎; 廣瀬 健太郎; 原 かおる; 金 政浩*; 北谷 文人; 小泉 光生; 中村 詔司; et al.
Nuclear Data Sheets, 119, p.61 - 64, 2014/05
被引用回数:19 パーセンタイル:75.79(Physics, Nuclear)Accurate determination of the neutron capture cross sections of radioactive nuclei is required in the fields of nuclear waste transmutation study and also nuclear astrophysics. The accurate neutron-nucleus reaction measurement instrument (ANNRI), which was installed in the materials and life science experimental facility (MLF) at the J-PARC, is expected to satisfy these demands. The capture cross section of Am was measured using a high efficiency Ge spectrometer installed in the ANNRI. By taking advantage of its high
-ray energy resolution, background components were precisely subtracted. The capture cross section of
Am was deduced for a neutron energy region between 0.01 and 20 eV. The obtained cross section and the Westcott factor are compared with the preceding experiments and evaluated values.
木野 幸一*; 古坂 道弘*; 平賀 富士夫*; 加美山 隆*; 鬼柳 善明*; 古高 和禎; 後神 進史*; 原 かおる; 原田 秀郎; 原田 正英; et al.
Nuclear Instruments and Methods in Physics Research A, 736, p.66 - 74, 2014/02
被引用回数:31 パーセンタイル:91.62(Instruments & Instrumentation)We studied the energy resolution of the pulsed neutron-beam of Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) at the Japan Proton Accelerator Research Complex/Materials and Life Science Experimental Facility (J-PARC/MLF). A simulation in the energy region from 0.7 meV to 1 MeV has been performed. Moreover, measurements have been done in the thermal and epithermal energies. The neutron energy resolution at ANNRI, which is determined by the time-of-flight technique, depends on the time structure of the neutron pulse. We obtained the neutron energy resolution as a function of the neutron energy by the simulation in the two operation modes of the neutron source: double and single bunch modes. In the double bunch mode, the resolution deteriorates above about 10 eV because the time structure of the neutron pulse splits into two peaks. The time structures at 13 energy points by measurements in the thermal energy region are in agreement with those of the simulation. In the epithermal energy region, the time structures at 17 energy points were obtained by measurements. The FWHM values of the time structures by the simulation and measurements are almost consistent. In the single bunch mode, the energy resolution is better than about 1% between 1 meV and 10 keV at the neutron source operation of 17.5 kW.
原 かおる; 後神 進史*; 原田 秀郎; 廣瀬 健太郎; 木村 敦; 金 政浩*; 北谷 文人; 小泉 光生; 中村 詔司; 藤 暢輔
JAEA-Conf 2013-002, p.161 - 166, 2013/10
For a pulse-height weighting technique, responses of two cluster Ge detectors with BGO anti-coincidence detectors have been measured at the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) in the Japan Proton Accelerator Research Complex (J-PARC). Co and
Cs standard sources were used for low-energy region (E
2 MeV). Prompt
-rays emitted from the
Cl(n,
)
Cl reactions were used for high-energy region (E
8 MeV). The measured spectra, peak efficiencies, and peak-to-total ratio were compared to simulations which were calculated by using the EGS5 code in the energy range 0.5-10 MeV. The response function will be applied to a data analysis in neutron capture reaction measurements at ANNRI.
廣瀬 健太郎; 古高 和禎; 原 かおる; 原田 秀郎; 木村 敦; 北谷 文人; 小泉 光生; 中村 詔司; 大島 真澄; 藤 暢輔; et al.
JAEA-Conf 2013-002, p.173 - 178, 2013/10
The cross section for Sn
reaction has been measured in the neutron energy from 1eV to 1keV using the ANNRI-NaI(Tl) spectrometer at J-PARC/MLF. The sample used in the present experiment was metal tin enriched in
Sn by 87%. The impurities of
Sn and
Sn were 9.3% and 3%, respectively. In the data analysis, the background of the frame-overlap neutrons and the scattered neutrons were subtracted. Comparison with the evaluation of JENDL-4.0 and ENDF/B-VII.1 will be presented in the poster session.
Ye, M.*; 黒田 健太*; 竹田 幸治; 斎藤 祐児; 岡本 和晃*; Zhu, S.-Y.*; 白井 開渡*; 宮本 幸治*; 有田 将司*; 仲武 昌史*; et al.
Journal of Physics; Condensed Matter, 25(23), p.232201_1 - 232201_5, 2013/06
被引用回数:12 パーセンタイル:48.54(Physics, Condensed Matter)トポロジカル絶縁体に磁性元素を入れると絶縁体表面に対して垂直方向に強磁性が発現するという理論研究があり、その実現は新しいスピントロにクス技術への足がかりになるものと期待されている。本研究では、トポロジカル絶縁体BiSe
の表面にFeを蒸着し、その磁性をFe L
吸収端における軟X線磁気円二色性で、電子状態を角度分解光電子分光を用いて調べた。磁気円二色性実験ではFeの膜厚依存性、試料表面に対する角度依存性測定も行った。その結果、いずれのFe膜厚(0.013-0.9ML)においても強磁性発現は確認できなかったものの、試料表面に垂直方向に磁気モーメントが向く強い磁気異方性を持った常磁性状態が確認された。また軌道磁気モーメントがFe膜厚の小さい試料において増大し、スピン磁気モーメントと軌道磁気モーメントの比率が強い膜厚依存性を示すこともわかった。この結果はトポロジカル絶縁体に対する磁性元素の量を調節することにより、磁性及び量子輸送現象を制御できる可能性を示すものである。
廣瀬 健太郎; 古高 和禎; 原 かおる; 原田 秀郎; 木村 敦; 金 政浩*; 北谷 文人; 小泉 光生; 中村 詔司; 大島 真澄; et al.
Journal of Nuclear Science and Technology, 50(2), p.188 - 200, 2013/02
被引用回数:28 パーセンタイル:89.52(Nuclear Science & Technology)J-PARC/ANNRIに設置したNaI検出器を用いて、Np
反応断面積を中性子エネルギー10meVから1keVにおいて測定した。断面積のエネルギー依存性は
B
反応をリファレンスとして求め、絶対値はJENDL-4.0評価済データを用い、第1共鳴で規格化することで得た。得られた熱中性子捕獲断面積は(176.7
4.7)bであった。また、
=25.3meVに対するマクスウェル平均断面積は(174.6
5.1)bであった。マクスウェル平均断面積を求める際、10meV以下での断面積はJENDL-4.0を参照した。これらの結果から、Westcottの
-factorとして0.988
0.010が得られた。これは最新のLANLの測定値0.944
0.035に比べ、約5%大きな結果である。
中村 詔司; 太田 雅之; 大島 真澄; 北谷 文人; 木村 敦; 金 政浩; 小泉 光生; 後神 進史*; 藤 暢輔; 原 かおる; et al.
JAEA-Conf 2012-001, p.147 - 152, 2012/07
The neutron capture cross section of Pd in the thermal-neutron energy region has been measured relative to the
B(n,
) reaction cross section by the neutron time-of-flight (TOF) method. The relative cross section was normalized to the average value calculated by the SAMMY code with JENDL-4.0 at the three energy points: 6.8 eV of
Pd, 11.8 eV of
Pd, and 33 eV of
Pd. Neutron-capture
rays were measured with a large Ge detector array called "4
Ge spectrometer", which is one component of the Accurate Neutron-Nucleus Reaction measurement Instrument (ANNRI) installed at the neutron Beam Line No.4 (BL04) of the Materials and Life science experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). This paper presents new findings on resonance assignments of
Pd, and the preliminary cross section.
木村 敦; 藤井 俊行*; 福谷 哲*; 古高 和禎; 後神 進史*; 原 かおる; 原田 秀郎; 廣瀬 健太郎; 堀 順一*; 井頭 政之*; et al.
Journal of Nuclear Science and Technology, 49(7-8), p.708 - 724, 2012/07
被引用回数:51 パーセンタイル:96.29(Nuclear Science & Technology)The neutron-capture cross sections of Cm and
Cm were measured in the energy range of 1-300 eV with an array of large germanium detectors in the ANNRI at J-PARC/MLF. The resonances at around 7.7 and 16.8 eV of
Cm and 4.3 and 15.3 eV of
Cm were observed in capture reactions for the first time. The uncertainties of the obtained cross sections are 5.8% at the top of the first resonance of
Cm and 6.6% at that of
Cm. Resonance analyses were performed for low-energy ones using the code SAMMY. The prompt
-ray spectra of
Cm and
Cm were also obtained. Eight and five new prompt
-rays emitted were observed in the
Cm(n,
) and
Cm(n,
) reactions, respectively.